Effect of low-light stress on nitrogen accumulation, distribution and grains protein content of Indica hybrid

A three-replicate, split-plot design was used with 3 species as main plot treatments and 3 light densities as the subplot treatments. Light treatments were under control, wrapped with one layers of 49%-shade and two layers of 69%-shade. Shading treatments began after 10% panicles heading. The plants dry weight, nitrogen content, yield and protein contents of grains were measured. The results of the experiment showed that the nitrogen contents were higher under low-light stress than control. The nitrogen content of leaves at 28d after shade increased 7.20%-25.23% relative to control, and the average nitrogen contents under low-light higher 36.57%-56.16% of stems and sheaths and 11.35%-29.89% of panicles than control. The protein content of grains increased significantly followed light densities decreased, and it was 14.62% higher under 49%-shade and 37.59% higher under 69%-shade. But the N accumulation amount per day decreased under low light. At the same time, the distribution rate of nitrogen to leaves, stems and sheaths increased, and to panicles decreased under low light. The export rate of the nitrogen from leaves, stems and sheaths and the import of the nitrogen to panicles under low light were lower than control. The grains protein yield under low light were significantly lower than control.